A trio of US Democratic congresswomen have criticized top tech firms' lack of diversity.

In an op-ed for The San Jose Mercury News, California Representatives Zoe Lofgren, Anna Eshoo and Barbara Lee called out Silicon Valley's technology houses for the low numbers of women and minorities in their ranks.

"It is painfully clear the sector faces a persistent and troubling deficit when it comes to women, African-Americans and Latinos," the trio wrote.

The congresswomen, who represent the congressional districts of the Bay Area's San Jose (Lofgren), Silicon Valley (Eshoo) and East Bay (Lee) regions, said that firms should provide greater transparency regarding the makeup of the workforces and seek to diversify their ranks with underrepresented groups, particularly at the boardroom and executive levels.

Recent diversity reports from major firms such as Google and Yahoo! show that technology firms are by and large staffed by white and Asian males, with leadership and technology-intensive jobs having particularly low numbers of women and minorities.

"Diversifying the tech workforce will not only boost the bottom line, but also provide African-American, Latino and female students with success stories in a field largely devoid of role models," they wrote.

To remedy the issue, the trio is calling for more resources to STEM education, particularly efforts to teach science and engineering to girls and in African American and Latino communities.

"Tech jobs are increasing, and with an average salary of $93,800 in 2012, they pay 98 per cent more than the average private sector wage," the Congresswomen wrote.

"But the number of students in STEM fields (science, technology, engineering and math) is far too low generally and it's dismal when it comes to women, Latinos and African-American students."

To be fair to Silicon Valley, however, it's worth noting that the industry's biggest brands are more diverse than least one group; Congress.

Yahoo!'s 23 per cent female executive team is better than Congress (18 per cent), while the 2.4 per cent Asian/Pacific Islander population of congress is dwarfed by the 30 per cent of Google's workforce which identifies as Asian.

Still, a bit of additional diversity and fresh perspective would be more than welcome in a market which has stagnated to the point of selling off public parking spots and potato salad.